Question 1

As currently understood, the ultimate source for the tremendous energy output of an AGN is:

Accepted Answer

A) nuclear fusion. 
B) nuclear fission. 
C) E = mc2. 
D) gravitational potential energy. 
A) nuclear fusion. 
B) nuclear fission. 
C) E = mc2. 
D) gravitational potential energy.

Question 2

Recent evidence indicates that quasars:

Accepted Answer

A) are isolated objects not associated with galaxies. 
B) occur only in elliptical galaxies. 
C) occur only in spiral galaxies. 
D) occur in both spiral and elliptical galaxies. 
A) are isolated objects not associated with galaxies. 
B) occur only in elliptical galaxies. 
C) occur only in spiral galaxies. 
D) occur in both spiral and elliptical galaxies.

Question 3

The flickering of an AGN allows one to calculate the size of the source. This is actually the size of the:

Accepted Answer

A) host galaxy. 
B) accretion disk around the black hole. 
C) event horizon of the black hole. 
D) central bulge of the host galaxy. 
A) host galaxy. 
B) accretion disk around the black hole. 
C) event horizon of the black hole. 
D) central bulge of the host galaxy.

Question 4

The surprising observational fact about quasars is that they appear to:

Accepted Answer

A) be the largest known structures in the universe, although they produce only modest amounts of energy. 
B) be moving rapidly toward us, while emitting large amounts of energy. 
C) be associated with ancient supernova explosions. 
D) produce the energy output of 1000 galaxies in a volume similar to that of our planetary system. 
A) be the largest known structures in the universe, although they produce only modest amounts of energy. 
B) be moving rapidly toward us, while emitting large amounts of energy. 
C) be associated with ancient supernova explosions. 
D) produce the energy output of 1000 galaxies in a volume similar to that of our planetary system.

Question 5

The typical optical spectrum of a quasar shows:

Accepted Answer

A) very redshifted emission lines superimposed upon a weak continuum of radiation. 
B) a series of very blueshifted emission lines, with no continuum component. 
C) a continuum of radiation crossed by a sequence of very redshifted absorption lines. 
D) a sequence of highly blueshifted absorption lines upon a continuum of radiation. 
A) very redshifted emission lines superimposed upon a weak continuum of radiation. 
B) a series of very blueshifted emission lines, with no continuum component. 
C) a continuum of radiation crossed by a sequence of very redshifted absorption lines. 
D) a sequence of highly blueshifted absorption lines upon a continuum of radiation.

Question 6

How do we measure or calculate the size of the black hole in the center of a quasar?

Accepted Answer

A) Observe a star moving around the black hole and use Kepler's third law to calculate the central mass. 
B) Measure directly the size of the dark area corresponding to the black hole. 
C) Use the Eddington radiation limit. 
D) Watch a star fall through the event horizon and measure its acceleration. 
A) Observe a star moving around the black hole and use Kepler's third law to calculate the central mass. 
B) Measure directly the size of the dark area corresponding to the black hole. 
C) Use the Eddington radiation limit. 
D) Watch a star fall through the event horizon and measure its acceleration.

Question 7

Blazars are:

Accepted Answer

A) elliptical galaxies whose nuclei resemble quasars. 
B) spiral galaxies whose nuclei resemble quasars. 
C) giant irregular galaxies that have neither spiral arms nor the smooth shape of elliptical galaxies. 
D) active galaxies, most of whose energy is emitted by two widely spaced radio lobes. 
A) elliptical galaxies whose nuclei resemble quasars. 
B) spiral galaxies whose nuclei resemble quasars. 
C) giant irregular galaxies that have neither spiral arms nor the smooth shape of elliptical galaxies. 
D) active galaxies, most of whose energy is emitted by two widely spaced radio lobes.

Question 8

The recessional velocity of a distant quasar is measured to be 60% of the speed of light. This speed is large enough that we must take relativity into account in computing its distance, which proves to be 3290 Mpc. Suppose we just use the Hubble law (without taking into account relativity); what is the result?

Accepted Answer

A) 779 Mpc 
B) 2470 Mpc 
C) 3290 Mpc 
D) 10,700 Mpc 
A) 779 Mpc 
B) 2470 Mpc 
C) 3290 Mpc 
D) 10,700 Mpc

Question 9

The hydrogen Balmer H $\alpha$ line with laboratory wavelength 656.3 nm is identified in emission in the spectrum of a quasar at 1968.9 nm. What is its redshift?

Accepted Answer

A) z = 0.3 
B) z = 1.0 
C) z = 2.0 
D) z = 3.0 
A) z = 0.3 
B) z = 1.0 
C) z = 2.0 
D) z = 3.0

Question 10

What is the end for a typical quasar?

Accepted Answer

A) The black hole at the center of the quasar pulls in more and more mass from the host galaxy until everything has fallen into the black hole and nothing visible remains. 
B) The tremendous inrush of matter at the Eddington limit produces a supernova explosion, leaving a galaxy with a halo of supernova remnants. 
C) The black hole eventually consumes all nearby fuel and becomes a dormant black hole, called a dead quasar, at the center of the still-functioning galaxy. 
D) Quasars are long lived, and we have no evidence on which to base a picture of how they end. 
A) The black hole at the center of the quasar pulls in more and more mass from the host galaxy until everything has fallen into the black hole and nothing visible remains. 
B) The tremendous inrush of matter at the Eddington limit produces a supernova explosion, leaving a galaxy with a halo of supernova remnants. 
C) The black hole eventually consumes all nearby fuel and becomes a dormant black hole, called a dead quasar, at the center of the still-functioning galaxy. 
D) Quasars are long lived, and we have no evidence on which to base a picture of how they end.

Question 11

Where does the name quasar come from?

Accepted Answer

A) It comes from quasarium, the name given to the new element that was identified with the spectral lines before these were recognized as hydrogen with a very large redshift. 
B) It is a contraction of "quasistellar radio source." 
C) It is a contraction of "quantum pulsar," the original name. 
D) It comes from Alfred 
A) It comes from quasarium, the name given to the new element that was identified with the spectral lines before these were recognized as hydrogen with a very large redshift. 
B) It is a contraction of "quasistellar radio source." 
C) It is a contraction of "quantum pulsar," the original name. 
D) It comes from Alfred

Question 12

A radio galaxy, viewed from a position so that the observer is looking down one of the jets toward the galaxy, is a:

Accepted Answer

A) blazar. 
B) quasar. 
C) Seyfert Type 1 galaxy. 
D) Seyfert Type 2 galaxy. 
A) blazar. 
B) quasar. 
C) Seyfert Type 1 galaxy. 
D) Seyfert Type 2 galaxy.

Question 13

An object with a diameter of 4 ly emits a sudden flash of light. On Earth this brightness change is seen to evolve over a period of:

Accepted Answer

A) 2 years. 
B) 4 years. 
C) 8 years. 
D) 16 years. 
A) 2 years. 
B) 4 years. 
C) 8 years. 
D) 16 years.

Question 14

Suppose a rotation curve is made of the region close to the center of a galaxy. At a distance of 4 pc from the center the radial velocity is 328 km/sec. How much mass is within this 4-pc radius (in solar masses)?

Accepted Answer

A) 106 
B) 108 
C) 2.4 × 1011 
D) 1.2 × 1017 
A) 106 
B) 108 
C) 2.4 × 1011 
D) 1.2 × 1017

Question 15

A blazar is a(n):

Accepted Answer

A) eclipsing binary star in which one component is believed to be a neutron star or a black hole. 
B) rapidly spinning neutron star. 
C) active galactic nucleus. 
D) emission nebula containing a young T Tauri star. 
A) eclipsing binary star in which one component is believed to be a neutron star or a black hole. 
B) rapidly spinning neutron star. 
C) active galactic nucleus. 
D) emission nebula containing a young T Tauri star.

Question 16

The apparent brightness of the quasar 3C 273 is b = 2.22 × 10-12 W/m2. Its distance, from the Hubble relationship, is 2 billion ly. What is its luminosity (in watts)?

Accepted Answer

A) 1036 
B) 1038 
C) 1040 
D) 1042 
A) 1036 
B) 1038 
C) 1040 
D) 1042

Question 17

The jets associated with AGN are defined by intense magnetic fields. What is the origin of these magnetic fields?

Accepted Answer

A) The stars that formed the black hole had magnetic fields, and the black hole retains those fields. 
B) The accretion disk contains a plasma of charged particles. The acceleration of these particles produces a magnetic field. 
C) The intense gravity of the black hole attracts and concentrates the magnetic field associated with the host galaxy as a whole. 
D) Friction between the inner and outer parts of the rotating accretion disk produce the magnetic fields. 
A) The stars that formed the black hole had magnetic fields, and the black hole retains those fields. 
B) The accretion disk contains a plasma of charged particles. The acceleration of these particles produces a magnetic field. 
C) The intense gravity of the black hole attracts and concentrates the magnetic field associated with the host galaxy as a whole. 
D) Friction between the inner and outer parts of the rotating accretion disk produce the magnetic fields.

Question 18

Where do Seyfert galaxies fit into the unified and accretion disk models for AGN?

Accepted Answer

A) Seyferts are young active galaxies that have not yet become quasars. 
B) Seyferts are former quasars that have become less active as a result of depletion of the source material needed to sustain the accretion disk around the central black hole. 
C) Seyferts are what we observe when looking at an active galaxy without jets. 
D) When an active galaxy has its accretion disk oriented so that the jets lie in the plane of the galaxy rather than perpendicular to it, the beams of synchrotron radiation can generate spiral arms, and the galaxy becomes a Seyfert. 
A) Seyferts are young active galaxies that have not yet become quasars. 
B) Seyferts are former quasars that have become less active as a result of depletion of the source material needed to sustain the accretion disk around the central black hole. 
C) Seyferts are what we observe when looking at an active galaxy without jets. 
D) When an active galaxy has its accretion disk oriented so that the jets lie in the plane of the galaxy rather than perpendicular to it, the beams of synchrotron radiation can generate spiral arms, and the galaxy becomes a Seyfert.

Question 19

The accretion disk around a typical quasar is about the size of:

Accepted Answer

A) the Sun. 
B) Earth's orbit. 
C) the solar system. 
D) the central bulge of the Milky Way Galaxy. 
A) the Sun. 
B) Earth's orbit. 
C) the solar system. 
D) the central bulge of the Milky Way Galaxy.

Question 20

The unusual feature that was noted in the optical spectra of the faint starlike objects that coincided in position with the intense sources of radio energy known as quasars was:

Accepted Answer

A) sets of spectral lines that indicated simultaneous motion of sources toward and away from the Sun, possibly a rapidly expanding shell of material around the radio source. 
B) the extreme redshift of emission lines that indicated high recessional velocities and hence great distances, requiring extremely high energy output in order to be detected. 
C) the extreme blueshift, meaning that these stars in our galaxy are coming toward Earth at very high velocities. 
D) the periodic variation of the Doppler shift from red to blue, indicating a light source oscillating back and forth over a few weeks. 
A) sets of spectral lines that indicated simultaneous motion of sources toward and away from the Sun, possibly a rapidly expanding shell of material around the radio source. 
B) the extreme redshift of emission lines that indicated high recessional velocities and hence great distances, requiring extremely high energy output in order to be detected. 
C) the extreme blueshift, meaning that these stars in our galaxy are coming toward Earth at very high velocities. 
D) the periodic variation of the Doppler shift from red to blue, indicating a light source oscillating back and forth over a few weeks.

Exam 24: Quasars and Active Galaxies

As currently understood, the ultimate source for the tremendous energy output of an AGN is:

Recent evidence indicates that quasars:

The flickering of an AGN allows one to calculate the size of the source. This is actually the size of the:

The surprising observational fact about quasars is that they appear to:

The typical optical spectrum of a quasar shows:

How do we measure or calculate the size of the black hole in the center of a quasar?

Blazars are:

The hydrogen Balmer H α\alphaα line with laboratory wavelength 656.3 nm is identified in emission in the spectrum of a quasar at 1968.9 nm. What is its redshift?

What is the end for a typical quasar?

Where does the name quasar come from?

A radio galaxy, viewed from a position so that the observer is looking down one of the jets toward the galaxy, is a:

An object with a diameter of 4 ly emits a sudden flash of light. On Earth this brightness change is seen to evolve over a period of:

Suppose a rotation curve is made of the region close to the center of a galaxy. At a distance of 4 pc from the center the radial velocity is 328 km/sec. How much mass is within this 4-pc radius (in solar masses)?

A blazar is a(n):

The apparent brightness of the quasar 3C 273 is b = 2.22 × 10-12 W/m2. Its distance, from the Hubble relationship, is 2 billion ly. What is its luminosity (in watts)?

The jets associated with AGN are defined by intense magnetic fields. What is the origin of these magnetic fields?

Where do Seyfert galaxies fit into the unified and accretion disk models for AGN?

The accretion disk around a typical quasar is about the size of:

The unusual feature that was noted in the optical spectra of the faint starlike objects that coincided in position with the intense sources of radio energy known as quasars was:

Astronomy and the Universe

Knowing the Heavens

Eclipses and the Motion of the Moon

Gravitation and the Waltz of the Planets

The Nature of Light

Optics and Telescopes

Comparative Planetology I: Our Solar System

Comparative Planetology II: the Origin of Our Solar System

The Living Earth

Our Barren Moon

Mercury, Venus, and Mars: Terrestrial, yet Unique

Jupiter and Saturn: Lords of the Planets

Jupiter and Saturns Satellites of Fire and Ice

Uranus, Neptune, Pluto, and the Kuiper Belt: Remote Worlds

Asteroids, Comets, and Impacts

Our Star, the Sun

The Nature of the Stars

The Birth of Stars

Stellar Evolution: on and After the Main Sequence

Stellar Evolution: The Death of Stars

Stellar Remnants: Neutron Stars and Black Holes

Our Galaxy

Galaxies

Cosmology: The Origin and Evolution of the Universe

Exploring the Early Universe

The Search for Extraterrestrial Life

Filters

The hydrogen Balmer H $\alpha$ line with laboratory wavelength 656.3 nm is identified in emission in the spectrum of a quasar at 1968.9 nm. What is its redshift?

The apparent brightness of the quasar 3C 273 is b = 2.22 × 10^-12 W/m². Its distance, from the Hubble relationship, is 2 billion ly. What is its luminosity (in watts)?